More than 800 suspected criminals have been arrested worldwide after being tricked into using an FBI-run encrypted messaging app, officials say.
The operation, jointly conceived by Australia and the FBI, saw devices with the ANOM app secretly distributed among criminals, allowing police to monitor their chats about drug smuggling, money laundering and even murder plots.
Officials called it a watershed moment.
Targets included drug gangs and people with links to the mafia.
Drugs, weapons and cash were also seized en masse in the operation.
Australian Prime Minister Scott Morrison said the operation had "struck a heavy blow against organised crime" around the world.
Europol described Operation Trojan Shield/Greenlight as the "biggest ever law enforcement operation against encrypted communication".
The FBI is expected to present more details later on Tuesday.